WO2001016622A9

WO2001016622A9 - Control of sources in survey operations

Info

Publication number: WO2001016622A9
Application number: PCT/US2000/040743
Authority: WO
Inventors: Harold L Longaker
Original assignee: Trimble Navigation Ltd
Priority date: 1999-08-31
Filing date: 2000-08-24
Publication date: 2002-05-10
Also published as: WO2001016622A1

Abstract

A method and apparatus for controlling vibroseis sources (10, 12, 14) in survey operations. A wireless local area network (50, 52, 54) establishing a communications link among vibroseis sources (10, 12, 14) operating in a group may enable the group to operate independent of a remote control unit (20) and may also provide a distributed system solution that mitigates communication difficulties between the sources (10, 12, 14) and the remote control unit (20).

Description

CONTROL OF SOURCES IN SURVEY OPERATIONS

FIELD OF THE INVENTION

This invention relates to the field of seismic data acquisition and, more specifically, to controlling sources used in seismic data acquisition operations.

BACKGROUND

In seismic surveying, acoustic energy waves are transmitted into the earth in order to map subterranean geological structures by measuring returned acoustic energy waves reflected from those geological structures. The subterranean geological layers create changes in the generated seismic waves due to refractions, reflections, and diffractions at the boundaries of each subterranean layer. Some of these altered acoustic energy waves return to the earth's surface to be measured by seismic sensors. Their arrival time is mainly dependent on the depth of the subterranean layers reflecting the vibrated wave.

In one type of seismic surveying operation, dynamite in a drilled shot hole, or shot point (SP), is used as the seismic energy source. A shooter proceeds from SP to SP firing off an installed dynamite charge on command from a central controller, or recorder.

Figure 1 illustrates another type of seismic surveying system that uses vibroseis truck groups to provide the source of the acoustic energy. The trucks in a vibroseis group generate ("vibrate") the acoustic energy waves at predetermined vibrator points ("VPs") usually marked with a stake placed by surveyors. During seismic survey operations, the vibroseis trucks typically navigate from VP to VP using these survey stakes.

In vibroseis operations, the acoustic energy waves vibrated by the vibroseis trucks are swept in frequency (frequency chirp) over a period of time, referred to as a sweep. The timing of the sweep among the vibroseis trucks within a group is tightly controlled. A typical vibroseis sweep may be a linear frequency sweep from approximately 10 Hz to 100 Hz and may have a duration on the order of 15 seconds.

-l- Acoustic energy waves returned to the earth's surface are measured and transmitted to a recorder. In a typical vibroseis operation, the returned waves are cross-correlated (pulse compression) with an image of the vibroseis sweep. The cross-correlated records are then recorded on to a tape. When dynamite is used as the seismic source there is no correlation process and the records are directly written to a tape. The tapes are sent to a data processor for analysis.

In both shooter and vibroseis operations, control of the operation is typically centralized at the recorder, with all events in the data generation and recording process being coordinated at the recorder. When a vibroseis truck group navigates to a VP, or a shooter to a SP, a communications link is established between each of sources (the vibroseis trucks or the shooter) and the recorder. In vibroseis truck groups, the communications link is typically in the form of an analog radio signal but in the case of the shooter it can also entail the use the field telemetry for the communications link. When the recorder is ready a handshaking process between the recorder and each of the sources (vibroseis trucks or shooter) takes place. When all the trucks are ready and the recorder is ready, a start to sweep command is sent from the recorder to the vibroseis trucks and the trucks perform a coordinated sweep. In shooter operations, the recorder sends a "fire" signal to a fire control box carried by the shooter.

After the sweep is completed, quality control reports are sent from each of the vibroseis trucks to the recorder. These quality reports include information about whether the vibroseis trucks actually performed a sweep, whether the sweeps were within specification, and, if equipped with GPS, the position of the truck at the time of the sweep. This cycle continues until the requisite number of sweeps for the occupied VP are completed. If a problem with a sweep is detected the recorder may command the vibroseis trucks to repeat the sweep. At the end of the last sweep for a VP the vibroseis trucks pick up their pads and proceed to the next VP.

In shooter operations, the quality control reports can be either recorded at the shooter or passed directly to the recorder. When using dynamite, there is only one shot per SP as the shot cannot be repeated until a new hole is drilled and loaded with dynamite.

One problem with seismic operations is that current system designs require the recorder to have positive control over the source operations (vibroseis truck group or shooters) in order for seismic survey production to proceed. Such a system design requirement dictates that there exists at all times a dependable wireless data link between the recorder and all the sources. Obstacles, distances, and environmental conditions may interfere with the radio link between the recorder and the sources. If the link with any one of the trucks in the vibroseis group or shooter fails, the survey operations are stopped until the link is reestablished.

For example, all the trucks in a vibroseis group must start their sweeps at the same time. If one or more of the trucks fails to get the start to sweep command and do not sweep, insufficient seismic energy may be imparted to the earth. Consequently the sweep might have to be repeated. Similarly, if all of the end of sweep quality reports from each vibroseis truck are not received by the recorder, progress may be impeded until the data is received. In shooter operations, if the link is not available the shot will not occur.

Another problem with prior survey operations is that the link used for transmitting quality control information of the vibroseis operation to the recorder may be at full capacity. Currently, there is a demand in the industry for increasing the amount of quality control information generated by a vibroseis truck. If the links are at full capacity, any additional information must be stored at the vibroseis trucks. This stored information cannot be immediately evaluated as the capability to evaluate the QC reports exists only at the recorder. Consequently stored QC information is usually only analyzed after operations have been completed for the day. However, problems detected at the end of a production day may be very expensive to rectify as they may require re- sweeping at a VP. The data acquisition systems in the above described operations operate on a synchronous basis. A synchronous based system creates an acoustic seismic wave on command and recovers all the data from that event before creating a subsequent seismic wave. As such, data recovery is synchronous with the vibroseis sweep or shooter's shot. Many of the current seismic data acquisition systems in use today operate in a synchronous manner.

In a synchronous system, the recorder is not ready to command a new sweep or shot until the data is recovered from the prior sweep. With these systems, if the communications link between the sources and the recorder is blocked then the operation is stopped. As such, a problem with current systems is that seismic sources cannot create a seismic wave when there is no positive communications link with the recorder.

In an asynchronous system, the data recovery is decoupled from the source operation: either the vibroseis sweep or shooter's shot. Consequently, the source can operate (sweep or shoot) when it is ready. After the source event, the time of the event is passed to the field boxes. The field boxes then pass the seismic data relating to that event time back to the recorder. This requires the field boxes to start recording some arbitrary amount of time before the event occurs. With this asynchronous method, the data is also sent to the recorder but there is no need for the system to wait to generate the next shot or sweep until the data from the prior source event has been recovered.

With an asynchronous system, there is no need for positive control of the shooter by the recorder because there is no reason to delay a sweep until the prior sweep's data is recovered. Consequently, sources can sweep without a command from the recorder. If a seismic source is to operate free of the recorder, certain functional requirements should be met. For both shooter and vibroseis operations these include self-generation of a time to sweep. For vibroseis group operations, coordination within a group is also required so that sources within a group: all sweep at the same time; record the exact time of the start of sweep; perform QA/QC checks for each sweep, and; take appropriate collective action if a QA/QC check fails. A problem with current systems is that the vibroseis trucks cannot self coordinate their operation independent of positive control by the recorder. An independent system would allow operations to proceed in the absence of a positive communications link between the recorder and the vibroseis trucks. SUMMARY OF THE INVENTION

The present invention pertains to a method and apparatus for controlling source operations. The method includes establishing a local area network between multiple sources, monitoring a status of each source, and transmitting the status on the local area network. The method may also include operating the multiple sources at a first position using the local area network and evaluating performance data of each of the sources, the performance data transmitted on the local area network. The method may also include having the multiple sources self determine a time of operation and promulgating the time of operation over the local area network.

Additional features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

Figure 1 illustrates a prior art land surveying system.

Figure 2 illustrates one embodiment of a survey operation.

Figure 3 illustrates one embodiment of a wireless local area network within a source group.

Figure 4 illustrates one embodiment of a flow of a survey operation using a local area network.

Figure 5 illustrates one embodiment of navigation procedures using a local area network.

Figure 6 illustrates one embodiment of time of sweep generation Figure 7 illustrates one embodiment of performance evaluation of a source group using a local area network.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth such as examples of specific information, frequencies, procedures, components, etc. in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that these specific details need not be employed to practice the present invention. In other instances, well known circuits or methods have not been described in detail in order to avoid unnecessarily obscuring the present invention.

A method and apparatus for providing a local area network for a source group is described. The local area network (LAN) may enable a distributed system solution that mitigates communication difficulties between the sources and a remote recorder by allowing for independent operation of the source groups. The method and apparatus described herein may be implemented with a wide variety of operations, including vibroseis survey operations. In one embodiment, the group of sources is a vibroseis truck group and the LAN is a wireless network. The wireless LAN may enable the vibroseis truck group to communicate to all trucks in the group the time to sweep, to initiate a sweep, to perform post sweep checks, and to navigate to a next sweep point independent of the remote recorder. It should be noted, however, that the method and apparatus is described in relation to vibroseis truck operations only for illustrative purposes and is not meant to be limited to vibroseis truck operations.

Figure 2 illustrates one embodiment of a survey operation. The survey operation (not drawn to scale) includes source groups 10, 12, and 14; the recorder 20; multiple VPs 30; multiple field boxes with geophone strings 35; and a telemetry link 40 connecting the field boxes 35 with the recorder 20. The sources within source groups 10, 12, and 14 are seismic energy generating devices. In one embodiment, the sources are vibroseis trucks. Each vibroseis truck within a source group lowers a pad to the ground that raises the truck. The vibroseis trucks then generate an acoustic energy wave by vibrating approximately in unison. In one embodiment, each source group 10, 12, and 14 includes four sources. Three source groups with four sources per source group are shown in Figure 2 only for illustrative purposes. In another embodiments, more or less sources and source groups may be used in survey operations.

Each source group 10, 12, and 14 may include a local area network 50, 52, and 54, respectively. The telemetry link 40 between the field boxes 35 and the recorder 20 is typically established using a cable but other types of communication links may also be used, for example, a radio link. A second telemetry link 25, for example, a radio link is established between the source groups 10, 12, and 14 and the recorder 20.

Each source within a source group 10, 12, and 14 generates acoustic energy waves at the predetermined VPs 30. Seismic detectors, for example, geophones, at the VPs 30 are used to measure acoustic waves returning from subterranean layers. The field boxes 35 include data acquisition systems that record the measured acoustics waves and store them in the form of digital data. This data is transmitted to the recorder 20 where it is stored to magnetic tape, usually after correlation with an image of the vibroseis sweep.

In one embodiment, source groups 10, 12, and 14 are vibroseis truck groups. In an alternative embodiment, source groups 10, 12, and 14 may be other types of seismic sources, for example, shooters firing off dynamite charges.

In one embodiment, vibroseis truck source groups 10, 12, and 14 navigate from VP to VP using a global positioning system (GPS). A GPS receiver in each of the vibroseis trucks computes the position of the vibroseis truck based on radio signals received from satellites orbiting the earth. While selective availability of these satellites and environmental conditions may degrade position signals to 100 meter accuracy, differential correction (DGPS) or real time kinematic (RTK) processes may be employed to increase accuracy to the within 1 meter to 2 centimeters, depending on the method used. RTK and DGPS both require the use of an additional radio frequency receiver for reception of additional data that is used to compute a corrected, more accurate, position. An additional GPS receiver and radio transmitter, referred to as a GPS base station, may be placed in recorder 20, which is positioned at a known location. The GPS base station broadcasts correction signals to the receivers (referred to as rovers) in each vibroseis truck. The rover receivers apply the correction signals for improved GPS positions. As such, the GPS enables the vibroseis trucks to determine their current position.

In one embodiment, each vibroseis truck within a source group 10, 12, and 14 is programmed in the form of a script file with position information of the VPs 30. Additionally each vibroseis source has a GPS unit providing the current position. The current position information of the vibroseis truck is used with the VP position information to permit a vibroseis truck to navigate to a next VP. In another embodiment, the vibroseis truck groups use survey stakes placed at each VP to navigate between VPs 30. The LANs 50, 52, and 54 within each source group 10, 12, and 14 enable the source groups 10, 12, and 14 to perform some operations independent of the recorder 20. In one embodiment, LANs 50, 52, and 54 are wireless LANs.

Figure 3 illustrates one embodiment of a wireless local area network within a source group. A wireless LAN is a network that does not use wires or fiber cables as the physical medium for the network. The wireless network 350 uses electromagnetic airwaves to communicate information from one point to another point without relying on any physical connections. The wireless LAN 350 includes transceivers within each of the sources 62, 64, 66, and 68 to transmit and receive data between the sources in source group 310. Data that is being transmitted is superimposed, or modulated, onto a carrier wave in a manner that allows it to be accurately extracted by a remote transceiver at one of the receiving sources. The close proximity of the sources 62, 64, 66, and 68 during operation may make transmissions on wireless LAN 350 highly reliable. In one embodiment, the wireless LAN 350 uses radio transmission as the physical medium. A narrowband radio system transmits and receives user data on a specific radio frequency kept as narrow as possible to pass the data. In other embodiments, other transmission technologies may be used, for example, spread spectrum and infrared technologies.

Spread spectrum technology uses a wideband radio frequency (RF) technique to encode data on RF waves. One type of spread spectrum technology, referred to as Direct Sequence Spread Spectrum (DSSS), generates a redundant pre-set bit pattern for each bit to be transmitted causing the RF transmission to be spread over a wide band of frequencies. The receiving source is provided with the pre-set code to decipher the transmission. The longer the bit pattern the greater the probability that the original data can be recovered. Even if one or more bits in the pattern are corrupted during transmission, statistical techniques embedded in the radio can recover the original data without the need for re-transmission.

To an unintended receiver, DSSS appears as low power wideband noise and is generally ignored. In one embodiment, a DSSS system at a frequency of approximately 2.4 GHz is used. A 2.4 GHz system may allow for operation in most countries without a license because many countries have an unlicensed frequency band around 2.4 GHz. In other embodiments, other frequencies are used, for example, approximately 900 MHz in the unlicensed ISM (Industrial- Scientific-Medical) band and approximately 5 GHz in the unlicensed National Information Infrastructure (Nil) band.

Spreading the transmission over a wide range of frequencies also provides increased protection against interference. Radio interference is likely to be only on one or a few frequencies within the spectrum used. When interference occurs, the wireless LAN 350 can reject the interfering transmission and receive the spread transmission. The wireless LAN 350 can also reject other spread transmissions which use a different pre-set code. If the interference is too great, the bit may be re-transmitted. If this interference is a persistent problem, the radios may be reconfigured to use a different frequency range. As such, with DSSS, data may be reliably transmitted even if the data signal is weaker than the background noise.

In another embodiment, infrared technology is used to transmit data in the wireless LAN 350. Infrared (IR) systems use high frequencies just below the visible light in the electromagnetic spectrum to carry data. Although IR cannot penetrate opaque objects, the close proximity of sources 62, 64, 66, and 68 within source group 310 may allow for line of sight operations.

It should be noted that wireless LANs are well known in the art; accordingly, a more detailed description of their properties and their operation is not provided herein. Wireless LAN components may be obtained from industry manufacturers, for examples, Proxim Inc., of California and RadioLAN Inc., of California.

In an alternative embodiment, a wired LAN may be used to establish a communications network within a source group. The operation of sources within a few feet of each other makes use of a wired network possible. The wired LAN may use one of various broadcast systems, for examples, ethernet, token ring, and fiber distributed data interface (FDDI). Wired LANs are well known in the art; accordingly, a more detailed description of their properties and their operation is not provided herein. In an alternative embodiment the telemetry of the field boxes may be in the form of a wireless LAN and the vibroseis trucks share this wireless network as their LAN.

Referring back to Figure 3, the wireless LAN 350 may be configured as a base-to-remote network. In a base-to-remote network one source in the source group 310 is selected as a hub source with the other sources being spoke sources. All communication between spoke sources, and between the recorder of Figure 2 and the spoke sources are routed through the hub source. In one embodiment, the source determined to have the best telemetry link 325 with the recorder of Figure 2 is selected as the hub source. In another embodiment, the hub source may be preselected. In an alternative embodiment, the wireless LAN 350 may be configured as a peer-to-peer network. Peer-to-peer networks permit direct communication between sources without going through a hub source.

Figure 4 illustrates one embodiment of a flow of a seismic survey operation using a local area network. A LAN is established between sources operating in a source group, step 410. The source group navigates to a designated VP using either pre-placed survey flags or onboard navigation using GPS. The trucks lower their pads in preparation for sweeping, step 420. The source group self-monitors its preparation status by transferring source information over the LAN, step 430. In one embodiment, a GPS unit on each source is used to determine that the source is at the correct VP and is within the specified distance to the VP. In another embodiment, survey flags are used and the system assumes that the sources are at the correct VP and are within specification.

The sources then self-determine when to begin sweep operations and synchronize the start of operations using the LAN, step 440. After the sources have completed their sweep, the sources self-evaluate their performance, step 450, and a decision is made whether the operation of the source group was within a predetermined specification, step 460. The performance information is transmitted to the recorder, steps 470 and 480, and action may be taken based on whether the source group passed the performance evaluation. In one embodiment, all sources within a source group exchange information over the LAN and the source having the best telemetry link with the recorder is selected to transfer performance information to the recorder. In another embodiment, when there is no current communication link to the recorder, the data is temporarily recorded and step 470 is delayed until the link is reestablished.

Figure 5 illustrates one embodiment of positioning procedures using a local area network. In one embodiment, a source group uses GPS signals and programmed VP position information to navigate to a designated VP for sweep operations. A source group receives position information, step 510, and timing information, step 520, from the GPS. With timing capabilities, each source group may synchronize the start of a sweep independent of a recorder. In one embodiment, each source includes a script file that contains VP position information, step 530. Based on the timing information and script file, the sources move to the next designated VP to perform another sweep, also independent of the recorder, step 540.

In another embodiment, one or more of the sources within a source group receives GPS correction messages from a GPS base station. These sources relay DGPS/RTK position corrections from the base station to all other sources within the group. In this manner, even if the DGPS/RTK link between the base station and one of the sources within the group fails, that source may still receive GPS corrections.

Figure 6 illustrates one embodiment of time of sweep generation and operation using a local area network. Each source within a group positions itself at a designated VP, step 610. Each source within the source group transmits status information on the LAN to a hub source. The status information indicates when a source is in position and ready to sweep, steps 620 and 630. In one embodiment, the hub source then verifies that each of the sources within the group is at the correct position and ready to sweep, step 640. With a script file and GPS capabilities, each source may perform its own position verification.

When all the sources are at a VP and ready to sweep (645), the sources communicate with each other using the LAN to synchronize the time at which the sweep will begin. When the hub source is ready and has received the ready signal from all the other sources in the group, the hub source will transmit a command or a time to sweep message on the LAN to initiate sweep operations, step 670. In this manner, the source group does not have to rely on a radio link to a recorder to receive sweep start commands. If sweep operations are initiated by the recorder, a faulty radio link with any one of the sources may prevent a coordinated sweep by all of the sources within a group. In one embodiment, the recorder coordinates multiple source group operations so that source generations of different source groups do not overlap in time. In one embodiment, the recorder is capable of disabling a source group from operating, step 650. The source group will not sweep if a halt command is received from the recorder instructing the source group not to sweep, step 660. In another embodiment, the recorder enables only a single source group to sweep at any given time. As long as a source group is enabled, it may sweep at any time based on its time information. However, if a source group is not enabled, the hub source in that group is prevented from generating a command to initiate a sweep.

In one embodiment, after a sweep has been initiated, the hub source transmits the time of sweep information to a field box, step 680, and the telemetry at the field box passes the information to the recorder and the other field boxes. In another embodiment, the hub source transmits the sweep information to the recorder and the recorder relays the information to the field boxes.

Figure 7 illustrates one embodiment of performance evaluation of a source group using a local area network. After a sweep is completed, each source conducts quality assurance (QA), also known as quality control (QC), checks to evaluate the performance of the source group (705). In one embodiment, the QC checks are performed by each source, rather than by the recorder. In one embodiment, the QC checks include a posteriori position verification, step 710. The QC checks also include verification that each source actually performed a sweep, step 720.

In another embodiment, the QC checks include an evaluation of whether individual source sweeps were performed according to a predetermined specification, step 730. The specification defines acceptable operating parameters for the sources. The QC information for a particular source is transmitted to the hub source over the LAN, step 740. Referring back to Figure 4, if all sources within a source group pass the QC check, the source group may transmit the QC information to the recorder, step 470. Source operations, however, may continue independent of a command from the recorder. The source group navigates to the next VP, step 420, and repeats the above described procedure.

If any of the sources within the source group fails a QC check, the QC information is transmitted to the recorder, step 480. In one embodiment, the information is evaluated by the recorder and corrective action may be taken before the source is permitted to continue operations, step 490. In another embodiment, a source group having a source failing a QC check automatically repeats sweep operations at the current VP before and if passes the QC check proceeds to the next VP.

By performing QA checks at the source and using a LAN to coordinate source group activities, survey operations may be maintained without a radio link between individual sources and the recorder provided that the data storage buffers in the field boxes are not full and the sources pass QA checks. As such, the LAN may allow for semi-autonomous operation and may eliminate the necessity of having a highly reliable radio link between the recorder and the sources.

In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

CLAIMSWhat is claimed is:

1. A method of source control, comprising:

(a) establishing (410) a local area network (50) among a plurality of sources (10);

(b) monitoring (430) a status of each of the plurality of sources (10),

(c) transmitting (620) the status on the local area network (50);

(d) operating (440) the plurality of sources (10) at a first position (30) using the local area network (50); and

(e) evaluating (450) performance data of each of the plurality of sources (10), the performance data transmitted on the local area network (50).

2. The method of claim 1, wherein monitoring a status comprises: determining (645) whether each of the plurality of sources (10) are at the first position (30); and determining (645) whether each of the plurality of sources (10) is ready for operation.

3. The method of claim 2, wherein operating the plurality of sources (10) comprises transmitting a start command (670) to each of the plurality of sources (10) on the local area network (50) at approximately the same time, the transmitting of the start command based on the status.

4. The method of claim 3, wherein operating the plurality of sources 10 further comprises: receiving position information (510) from an external source by the plurality of sources (10); receiving timing information (520) from the external source by the plurality of sources (10); and synchronizing operation of the plurality of sources (10) with each other based on the timing and position information.

5. The method of claim 3, wherein evaluating performance data comprises: generating a result data (705) for each of the plurality of sources (10), the result data indicating whether a source of the plurality of sources (10) performed within predetermined operating parameters; and notifying (740) at least one of the plurality of sources (10) of the result of each of the plurality of sources (10).

6. The method of claim 5, further comprising repeating steps (a) through (e) at a second position if the plurality of sources (10) performed within the predetermined operating parameters.

7. The method of claim 5, further comprising repeating steps (a) through (e) at the first position if the plurality of sources (10) did not perform within the predetermined operating parameters.

8. The method of claim 5, wherein the plurality of sources (10) are not operated if a stop command is received by one of the plurality of sources (10) from a recorder (20).

9. The method of claim 6, wherein the sources (10) navigate (540) to the second position (30) using a global positioning system.

10. The method of claim 5, further comprising transmitting the result data (680) to a recorder (20).

11. A source group operation system, comprising: a plurality of sources (10) to operate at a first position (30); a local area network (50) coupled to the plurality of sources (10), the local area network (50) to transmit data between the plurality of sources (10); and a recorder (20) coupled to the plurality of sources (10) to receive performance information from each of the plurality of sources (10), the performance information generated by each of the plurality of sources (10).

12. The operation system of claim 11, wherein one of the plurality of sources (10) is a hub source (68) and wherein each of the plurality of sources (66) transmits status information to the hub source (68).

13. The operation system of claim 12, wherein each of the plurality of sources (10) has a positioning system and a timing system to navigate to the first position (30).

14. The operation system of claim 13, wherein the status information includes position data and wherein the status information identifies whether each of the plurality of sources (10) is ready to operate.

15. The operation system of claim 14, wherein the hub source (68) transmits a start command to the plurality of sources (10) if the plurality of sources (10) are at the first position (30) and ready to operate, the start command transmitted at a first time, the start command transmitted independent of the recorder (20).

16. The operation system of claim 15, wherein the performance information includes data indicating whether a source (10) performed within predetermined operation parameters.

17. The operation system of claim 16, wherein the plurality of sources

(10) operate at a second position (30) if the plurality of sources (10) performed within the predetermined operation parameters.

18. The operation system of claim 16, wherein the plurality of sources (10) operate at either the first position (30) or the second position (30) at a second time based on a command received from the recorder (20).

19. The operation system of claim 16, wherein the local area network (50) is a wireless network.

20. The operation system of claim 15, further comprising a data acquisition system (35) coupled to the plurality of sources (10) to receive the first time, the data acquisition system (35) to transmit the first time to the recorder (20).

21. The operation system of claim 20, wherein the local area network (50) is a wireless network.

22. The operation system of claim 21, wherein the data acquisition system (35) transmits the first time asynchronous with receiving the first time from the plurality of sources (10).

23. A method of source control, comprising: establishing (410) a local area network (50) among a plurality of vibroseis sources (10); and operating (440) the plurality of vibroseis sources (10) independent of a remote control unit (20) using the local area network (50).

24. The method of claim 23, further comprising: monitoring (430) a status of each of the plurality of vibroseis sources (10), the status transmitted on the local area network (50); and evaluating (450) performance data of each of the plurality of vibroseis sources (10) independent of the remote control unit (20), the performance data transmitted on the local area network (50).

25. The method of claim 23, wherein operating (440) the plurality of vibroseis sources (10) comprises synchronizing a start of an operation of the plurality of vibroseis sources (10) with each other based on data, the data transmitted over the local area network (50).

26. The method of claim 25, wherein operating (440) the plurality of vibroseis sources (10) further comprises evaluating a performance of each of the vibroseis sources (10) independent of the remote control unit (20).